According to matrix algebra, I cannot subtract a vector from a matrix, because they don't have the same size.
I want to notate that every column of $R_i^t$ is subtracted by vector $R_f^t$, but I don't want to either merge them into 1 matrix, nor change the vector to matrix in order to emphasise the nature of the variables.
Given matrix $\mathbf A \in \mathbb R^{n \times p}$, we can subtract vector $\mathbf b \in \mathbb R^n$ from all $p$ columns of $\bf A$ via $\color{blue}{\mathbf A - \mathbf b {\bf 1}_p^{\top}}$.